Abstract
INTRODUCTION: Loss of synapses best correlates to cognitive deficits in Alzheimer's disease (AD) in which oligomeric neurotoxic species of amyloid-β appears to contribute synaptic pathology. Although a number of clinical pathologic studies have been performed with limited sample size, there are no systematic studies encompassing large samples. Therefore, we performed a meta-analysis study. METHODS: We identified 417 publications reporting postmortem synapse and synaptic marker loss from AD patients. Two meta-analyses were performed using a single database of subselected publications and calculating the standard mean differences. RESULTS: Meta-analysis confirmed synaptic loss in selected brain regions is an early event in AD pathogenesis. The second meta-analysis of 57 synaptic markers revealed that presynaptic makers were affected more than postsynaptic markers. DISCUSSION: The present meta-analysis study showed a consistent synaptic loss across brain regions and that molecular machinery including endosomal pathways, vesicular assembly mechanisms, glutamate receptors, and axonal transport are often affected.